trying to do: boost::detail::atomic_count c(0); std::cout << long(c) << std::endl; with gcc 3.2.2 gives: /usr/include/boost/detail/atomic_count_gcc.hpp: In member function `boost::detail::atomic_count::operator long int() const': /usr/include/boost/detail/atomic_count_gcc.hpp:46: invalid conversion from ` const _Atomic_word*' to `volatile _Atomic_word*' in the following function: operator long() const { return __exchange_and_add(&value_, 0); } The problem can be solved by making the private member "_Atomic_word value_" mutable. renej ps I know I shouldn't use detail/* stuff directly... --